A distant Martian campfire? The first of many streetlights to come on the red planet? Or, perhaps an alien hiker's mirror sending out a SOS signal?

Probably none of the above, but the imagination could have some fun with wild speculation. More than likely, according to NASA scientists, it's merely a reflection of sunlight bouncing off the surface of a rock at just the right angle. Either way, it has recently added some excitement to planetary exploration.

The unusual photograph, in which a small speck of light can be seen on the left-handed horizon, was captured on two different occasions with the Curiosity rovers cameras.